1. Field of the Invention
The present invention relates to driving of servo motors, and more particularly, to a feedback switching device and method that allow to actively switch the feedback mode in accordance with the rotating speed of a servo motor.
2. Description of Related Art
Servo motor drivers have been widely applied in modern industries and developed towards high performance, multi-function and low cost. In some application, a servo motor must operate within a wide speed range, and how to build up a speed control architecture is critical to effectively improving the performance and reducing the cost of the servo motor driver.
For example, a designer can use a position sensor such as an encoder or a resolver to build up the speed control architecture for a servo motor. That is, the designer builds up the speed control architecture through a position sensing feedback technology. In such a case, when the servo motor operates at a low rotating speed, the servo motor driver can correctly receive a position signal as long as the bandwidth of the position signal is lower than that of the position sensor. On the other hand, if the servo motor operates at an extra-high rotating speed such that the bandwidth of the position signal is higher than that of the position sensor, the position signal will be distorted. To solve the problem, a sensorless position estimation feedback technology has been developed, which can be applied in a high-speed servo motor to estimate the motor angle, thereby building up the speed control architectures for the high-speed servo motor.
However, before a servo motor operates, the user must determine which one of the position sensing feedback technology and the sensorless position estimation feedback technology is to be used for building up the speed control architecture, and during the operation of the servo motor, the speed control architecture preset by the user cannot be flexibly changed in accordance with the rotating speed of the servo motor. As such, the servo motor driver cannot precisely control the servo motor. In particular, if the position sensing feedback technology is used to build up the speed control architecture, when the rotating speed of the servo motor is higher than a certain value, the position signal obtained through the position sensing feedback technology will be distorted. Therefore, the servo motor driver cannot obtain correct position information. On the other hand, if the sensorless position estimation feedback technology is used to build up the speed control architecture, when the rotating speed of the servo motor is lower than a certain value, the position signal obtained through the sensorless position estimation feedback technology is of low precision. As such, the servo motor driver also cannot obtain correct position information.
Therefore, there is a need to provide a feedback switching device and method for driving of a servo motor so as to overcome the above-described drawbacks.